Photographic developing apparatus



Aug. 8, 1967 M. FRIEDEL PHOTOGRAPHIC DEVELOPING APPARATUS Filed Feb. 2,1965 FIG! INVENTOR. MURRAY FR IEDEL FIG. 2

United States Patent ice 3,334,566 PHOTOGRAPHIC DEVELOPING APPARATUSMurray Friedel, North Miami Beach, Fla, assignor to Visual GraphicsCorp, New York, N.Y., a corporation of New York Filed Feb. 2, 1965, Ser.No. 429,750 1 Claim. (Cl. 95-89) ABSTRACT OF THE DISCLOSURE Apparatus,responsive to the passage of a sheet of photographic materialtherethrough, for adding processing chemicals to a processing bath inorder to maintain the bath at a constant strength throughout continuedoperation of the processor.

This invention relates to photographic developing apparatus. Inparticular, this invention relates to photographic developing apparatusequipped with means for automatically maintaining processing solutionsat proper strength.

In many photographic processing operations, it becomes a problem tomaintain the concentration of the various processing solutions at properstrength. This is particularly a problem with respect to the developersolution, the function of which is to reduce to metallic silver thosegrains of silver halide in the emulsion that have been previouslyactivated by the absorption of light energy.

This chemical reduction or development process must be carefullycontrolled with respect to a number of variables. In the usual practice,the initial exposure is controlled so as to give a latent image which,when processed under standard conditions, will develop to the properdensity. Obviously, if the conditions are other than standard, the imagewill be either over or underdeveloped, and the image qualitycorrespondingly poor. The most important variables in the processingoperation are time, temperature and the concentration of the solution.

The time of development is easily controlled by a variety of well knownmechanical means, or may be controlled manually by the operator with theaid of a timer.

Similarly, control of the processing temperature ordinarily presents noparticular difficulty. Control of the concentration of the developed,however, is more of a problem. Being a reducing agent, the developer issubject to oxidation by the atmosphere, and such oxidation consumes thereducing agents, lowering the effective concentration of the solution.Also, each piece of photographic material (film, paper, etc.) that isprocessed consumes a portion of the reducing agents in the developer sothat the developer gradually becomes exhausted.

The traditional approach to the problem of keeping the developerstrength constant within reasonable limits has been to use large volumesof solution, protecting them so far as possible against atmosphericoxidation, and to limit the number of pieces processed by a given batchso that the effective concentration of the developer does not varyappreciably between the first and the last piece processed. Thisapproach is wasteful in that, if the concentration of the solution whendiscarded was substantially the same as its concentration when fresh,large amounts of unused reductant are necessarily discarded.

The problem of maintaining developer concentration is particularly acutein connection with certain more recent types of photographic processingequipment, in which the reservoir of processing liquid is a chamberformed by a plurality of contiguous rollers. In order to make a liquidtight seal, such rollers must be made and mounted to close tolerances.This fact adds to their cost,

3,334,566 Patented Aug. 8, 1967 the the difficulty and expense ofconstructing such apparatus mount sharply as the size increases. Moreover, processing apparatus of this type is frequently designed forapplications requiring compactness, such as use aboard spacecraft andthe like. In keeping such apparatus small, whether for cost or end-userequirements, it is necessary to make the reservoir of processing fluidcorrespondingly small. This, in turn, aggravates the diificultiesmentioned above, and makes it more difiicult to maintain the effectiveconcentration of the processing solution. An object of the invention isto provide improved apparatus for developing photographic materials.

Another object is to provide apparatus for automatically maintaining theconcentration of photographic processing solutions.

Another object is to provide a photographic processing apparatus whichmakes more efiicient usage of processing chemicals, and wastes less ofsuch chemicals than apparatus and methods heretofore proposed.

A further object is to provide means for effectively maintaining theconcentration of processing solutions in apparatus using small volumesof such solutions.

A feature of the present invention is the use of sensing means to signalthe passage of a sheet of photographic material to or through aprocessing machine.

Another feature is the use of dispensing means for delivering repeatedsmall, controlled increments of processing chemicals to a reservoir ofprocessing solution.

Still another feature is the use of sensing means for signaling theapproximate size of a piece of photographic material being processed,and dispensing means responsive to said sensing means; for adding anincrement of processing chemical to a reservoir of processing solution,said increment being approximately proportioned to the amount ofprocessing chemical consumed by the processing of said piece ofphotographic material.

The invention consists of the construction, combination and arrangementof parts, as herein illustrated, described and claim.

In the accompanying drawing, forming a part hereof is illustratedseveral embodiments of the invention, and in which:

FIGURE 1 is a somewhat diagrammatic view, partly in perspective andpartly in central cross-section of an apparatus according to oneembodiment of the invention.

FIGURE 2 is a fragmentary perspective view of the sensing meansaccording to a slight different embodiment of the invention.

FIGURE 3 is a central cross-section of a photographic processingapparatus according to another embodiment of the present invention.

Referring now more particularly to FIGURES 1 and 2, the apparatuscomprises sensing means in the form of fingers 10, which normally ridein channels 11 cut in roller 12. Roller 12 may be simply a part of thesensing system, but for economy of construction, it is generally made apart of the feed system whereby the sheet mate rial is fed into theapparatus. As a sheet of photographic material 13 is fed into theapparatus, it lifts one or more fingers 10 out of their respectivechannels 11, closing an associated switch 14. Switch 14, in turn,signals a variable impulse control 15, which transmits an impulse tocontrol means represented by solenoid 16. Solenoid 16, through asuitable linkage represented by lever 17, pivoted at 18, momentarilyopens an appropriate dispensing valve such as needle valve 19, whichallows the flow of a controlled increment of processing chemicalsolution 20 out of a supply tank 21 into the working reservoir ofprocessing solution (not shown in these figures).

In the preferred embodiment of the invention, there are provided aplurality of sensing fingers 10 in side-by-side parallel relationship,each riding in its own respective channel 11. Each of the sensingfingers actuates a switch 14, and each of switches 14 feeds a separatechan nel inthe variable impulse control 15.

The variable impulse control is an assembly of conventional circuitryresponsive to two characteristics of the input signals: (1) the numberof channels activated (i.e. the number of sensing fingers 10, lifted bythe incoming sheet material) and (2) the length of time for which eachchannel is activated. These responses can be achieved in a variety ofways. In one convenient arrangement the variable impulse controlincludes a clock circuit which periodically samples each of the sensingchannels. Such a clock circuit may, for example, make contact with eachof five sensing channels for one-fifth of a second each second. Theclock circuit may feed the received impulse signals into a delay line ordirectly to the solenoid 16 (through an amplifier if desired) so thateach pulse sensed from the sampling of the sensing fingers causes thesole noid to open valve 19 for a discrete interval, thereby dispensing acontrolled increment of processing chemical solution 20.

The solenoid may of course, if desired, be preceded by a counter, andopen the valve only once for a predetermined number of impulses, ratherthan opening it in response to each impulse.

The concentration of the processing chemical solution and the durationof the period during which the valve is opened in response to eachimpulse should be chosen so as to keep the effective concentration ofthe processing bath substantially constant. In this respect, it may beobserved that (neglecting the effect of atmospheric oxidation) thedepletion of the effective strength of the processing solution arisesfrom two sources: (1) the depletion of reductant values by chemicalreaction with the material being processed, and (2) mechanical removalfrom the bath of solution which has soaked into the material beingprocessed. Both of these sources of depletion are proportional to thearea of the sheet material being processed.

Atmospheric oxidation may be disregarded for all practical purposes,because of the fact that the solution is continually being replenished,so that the effect of atmospheric oxidation is easily compensated for byslightly correcting upwardly the size of the increment of processingchemical dispensed in response to each impulse.

In order to keep the volume of the bath constant, the apparatus shouldbe adjusted so that the volume of makeup solution added is substantiallyequal to the volume of solution mechanically removed by the sheetmaterial as it is discharged. This is easily accomplished, bearing inmind that: (1) the volume of solution dispensed as makeup, and theamount of solution mechanically removed from the processing bath, areboth proportional to the area of the sheet material being processed;and, (2) the sensing means is responsive to the area of the sheetmaterial, because the number of impulses is proportional to the productof the length and the width (and hence the area) of the sheet material.

Fine adjustments to the mechanism are generally most easily andeffectively made by periodically checking the concentration and level ofthe processing solution in the actual processing bath, rather than bycalculating the proper settings a priori. Thus, the apparatus isinitially set to deliver a volume of solution approximately equal tothat mechanically removed in processing, and at an effectiveconcentration approximating that of the initial charge to the processingbath. After the apparatus has run for a moderate period of time, theliquid level in the processing bath is checked, as is the effectiveconcentration thereof. (By the term effective concentration is meant theconcentration of active reductant, disregarding the presence of spentreductant in the solution.)

If the volume of the liquid in the processing bath tends to decrease, itindicates that the volume of liquid removed mechanically, as liquidsoaked into the sheet material, is greater than the volume of theincrement of solution added in response to the sensing means. In such acase, the length of the pulse may be increased, or the value may beadjusted to deliver a greater volume of liquid at each pulse. Similarly,if the tendency is for the volume of the processing bath to increase,the pulse may be shortened or the valve may be adjusted to deliver asmaller volume of solution for each pulse.

If the volume remains constant (after any necessary adjustment, as justdescribed) but the solution in the processing bath becomes progressivelymore or less concentrated, the situation is easily compensated byrespectively decreasing or increasing the concentration of the makeupsolution.

It may be noted that it is ordinarily not necessary to perform chemicaltests in order to detect changes in the concentration of the solution(although chemical tests may be used, if desired). Normally, theoperator is able very readily to detect a weak or an overly strongdeveloper merely by observing the condition of the processed material asit emerges from the machine.

In this way, by merely observing the changes, if any, in the volume ofthe processing solution and in the degree of development of theprocessed sheet material, the operator can make small adjustments asneeded and keep the processing solution at substantially constant,optimum strength.

If desired, even these observations and adjustments can be readilyauto-mated, by interposing concentration and volume sensing means andadjusting means in the form of a feedback loop which, however, is not apart of the present invention.

FIGURE 3 illustrates in central cross-section, one type of photographicprocessing apparatus to which the present invention is applicable. Inthe apparatus according to FIGURE 3, a plurality of processing baths 22are provided, each bath consisting of a body of liquid processingchemical solution or the like, contained in a reservoir formed by theV-shaped trough between a pair of contacting rollers, together withsuitable end-plates (not shown) to close the ends of the troughs.

In the apparatus according to this embodiment of the invention, thevarious solutions are arranged in a vertical array, and the sheet ofphotographic material 13 enters at the top and passes downwardly throughthe various processing baths in turn. The processing baths may be, in atypical case, a developer solution 23, a stop-bath 24, and a fixer 25such as sodium thiosulfate solution, in order named, proceeding from topto bottom.

At it is fed into the apparatus, the sheet material 13 initially passesover roller 12, lifting fingers 10 out of channel(s) 11 as it goes.Sensing fingers 10 are connected to switches 14, which transmit signalsto a variable impulse control 15, which in turn controls a dispensingvalve 19, as illustrated in FIGURE 1, and dispensing valve 19 controlsthe addition of makeup solution to at least one of processing baths 22.Normally, the first processing bath 22 is the one which contains thedeveloper solution, and this will be replenished by a :makeup systemresponsive to sensing fingers 10. If desired, the other processing bathsmay also be replenished in the same way, but the concentratiion of theother baths, such as the stop bath and the fixer are not as critical.For this reason, it may be found more desirable from an economicstandpoint to provide for automatic control of only the developer, andrely on the operator to maintain an adequate concentration of processingchemicals in the other baths. In some applications, however, such as theprocessing of color film, precise control is required to be maintainedon the concentration of several processing solutions. Where this is thecase, the variable impulse control may be connected to a number ofdispensing valves, each serving to replenish a different processingbath.

As the sheet material is fed into the apparatus of FIG- URE 3, afterpassing between roller 12 and sensing fingers 10, it is deflecteddownwardly by flange 26 into the nip between the rolls, and is carriedthrough the successive processing baths 22, as indicated by the dashedline and arrows.

The present invention, as above described, provides improved apparatusfor developing photographic materials. In particular, it providesimproved apparatus for maintaining a constant concentration inphotographic processing solutions. The apparatus of this invention makespossible more efiicient usage of processing chemicals, and minimizeswaste of these materials. It is capable of automatically maintaining aconstant effective concentration of processing chemicals, even in bathsof very limited volume.

While this invention has been described with reference to certainpreferred embodiments and illustrated by way of certain drawings, theseare illustrative only, and many alternatives and equivalents willreadily occur to those skilled in the art, without departing from thespirit and proper scope of the present invention.

Having thus fully described the invention, what is claimed as new anddesired to be secured by Letters Patent of the United States is:

Apparatus for controlling the addition of processing chemicals to aphotographic processing bath, said apparatus comprising in combinationmeans for sensing the passage of a sheet of photographic material tosaid bath comprising a roller having a circumferential channel, apivotally mounted sensing finger normally resident in said channel andsubject to be lifted out of said channel by the passage of a sheet ofphotographic material over said roller, and an electrical switchresponsive to the position of said sensing finger, means responsive tosaid sensing means for generating a timed series of spaced electricalpulses throughout the time said sensing means is activated by suchsheet, a reservoir of processing chemical and valve means controllingthe flow of processing chemical from said reservoir to said processingbath, said valve means being responsive to said electrical pulses topermit the flow of a predetermined increment of processing chemical fromsaid reservoir into said processing bath in response to a predeterminednumber of said pulses.

References Cited UNITED STATES PATENTS 2,446,668 8/1948 Tuttle et al -892,778,734 1/ 1957 Fairbank. 2,837,988 6/1958 Pavelle 95-89 3,142,2427/1964 Erikson 95-89 3,202,072 8/1965 Limberger 95-89 NORTON ANSHER,Primary Examiner. F. L. BRAUN, Assistant Examiner.

